The present invention relates to novel bicycloheptane derivatives useful as intermediates for the production of agricultural chemicals, drugs and others, and to processes for the preparation of the same.
A Diels-Alder reaction of trans-methyl crotonate with 1,1-dimethoxy-2,3,4,5-tetrachlorocyclopentadiene is described in Tetrahedron 42, 1741-1744 (1986). It is reported that the addition product becomes a mixture of isomers that are difficult to separate by distillation. A reaction with ethyl crotonate is also described in J. Org. Chem., 26, 2066 (1961).
There are no reports in known documents, patents and others on a reaction with crotonaldehyde instead of methyl crotonate described in the above-mentioned paper. If the reaction is carried out under the same conditions as those described in the said paper, a main product is the trans-2 isomer, as shown in the following reaction scheme. The trans-1 and cis isomers, which are preferable to use as intermediates for producing herbicides, were obtained at low production rates. (A rough isomer ratio was trans-1:cis:trans-2=20:10:70.) 
The present invention relates to novel bicycloheptane derivatives to become intermediates for the preparation of drugs, agricultural chemicals and others, and to processes for the production of the same. It is an object of the present invention to provide compounds to be used for the preparation of trans-1 and cis isomers suitable for the purposes in good yields, and industrially advantageous processes.
The trans-1 and cis isomers are compounds to be used as intermediates for the industrially advantageous production of bicycloheptene compounds represented by Formula (3) 
(wherein, Het is optionally substituted isoxazolyl or isoxazolidyl). The compounds of Formula (3) are useful as intermediates for the preparation of herbicides described in World Open WO 97/41117, WO 98/31681 and others.
The compounds of the present invention may have stereoisomers, depending on substituents at positions 5 and 6. The (1S, 4R, 5R, 6S) and (1R, 4S, 5S, 6R) isomers are represented by xe2x80x9ctransxe2x80x9d and (1S, 4R, SR, 6R) and (1R, 4S, 5S, 6S) isomers as xe2x80x9ccisxe2x80x9d.
The present invention relates to compounds of Formula (1) 
(wherein, X is hydroxycarbonyl, hydroxymethyl, halogenomethyl, nitromethyl or methylthiomethyl), and processes for the preparation of the said compounds of Formula (1) by reactions of 5,5-dimethoxy-1,2,3,4-tetrachlorocyclopentadiene with compounds of Formula (2)
CH3CHxe2x95x90CHxe2x80x94Xxe2x80x83xe2x80x83(2)
(wherein X is as defined above).
The processes of the present invention also give mixtures of trans and cis isomers, as shown in the following reaction scheme. However, the trans-2 isomer is produced at a very low 
rate, as described later in Examples. The compounds of the present invention are thus produced industrially advantageously.
Preparation of trans-1,4,5,6-tetrachloro-3-methyl-7,7-dimethoxybicyclo[2.2.1]-hept-5-ene-2-carboxylic acid, where X is a carboxylic acid. 
A Diels-Alder reaction of (E)-2-butenic acid and 5,5-dimethoxy-1,2,3,4-tetrachlorocyclopentadiene is carried out by heating at 120 to 160xc2x0 C. without a solvent for 8 to 15 hours.
The reaction product consists of the main product of (1) and small amounts of Stereoisomers (2) and (3). Stereoisomer (1) is isolated by recrystallization of the reaction product. Examples of solvents to use for the recrystallization include general recrystallization solvents, such as n-hexane, acetone, ethyl acetate or their mixtures.
Preparation of cis-1,4,5,6-tetrachloro-3-methyl-7,7-dimethoxybicyclo[2.2.1]-hept-5-ene-2-carboxylic acid, where X is a carboxylic acid. 
A Diels-Alder reaction of (Z)-2-butenic acid and 5,5-dimethoxy-1,2,3,4-tetrachlorocyclopentadiene is carried out by heating at 100 to 120xc2x0 C. without a solvent for 8 to 15 hours.
The reaction product consists of the main product of (2) and small amounts of Stereoisomers (1) and (3). Stereoisomer (2) is isolated by recrystallization of the reaction product from a general recrystallization solvent, such as n-hexane, acetone, ethyl acetate or their mixture.
A mixture containing a larger amount of either the (E)-or (Z)-2-butenic acid can also be used as a starting material for Processes 1 and 2.

(wherein, Xxe2x80x2 is hydroxymethyl, halogenomethyl, nitromethyl or methylthiomethyl).
X of Compound (1) of the present invention can be any substituent that is oxidized toxe2x80x94CHO or nitrile oxide. Examples of X include hydroxymethyl, chloromethyl, bromomethyl, nitromethyl and methylthiomethyl.
A solvent may or may not be used for the reaction. A reaction temperature is about that necessary for the reaction to proceed, and is usually selected in the range between 100xc2x0 C. and 200xc2x0 C. Any solvent inert to the reaction can be used. Alcoholic solvents such as methoxy ethanol and amyl alcohol are preferred. A reaction time varies depending on compounds used. It takes about 5 hours to a week.
Usual wark-up after the completion of the reaction give target compounds.
Reaction products are identified by 1R, NMR, MS and other means.